Crosslinked P84 copolyimide/MXene mixed matrix membrane with excellent solvent resistance and permselectivity

MXene is a novel 2D lamellar material with excellent hydrophilicity and permselectivity. MXene was introduced in the P84 polymer matrix and the matrix was crosslinked with triethylenetetramine(TETA) to improve the permselectivity and solvent resistance of the polyimide membrane. The membrane was characterized with SEM, AFM and ATR-FTIR, and effects of MXene content on the membrane morphology and separation performance are investigated. The membrane prepared with 18% P84 and 1% MXene shows high rejection(100%) to gentian violet(408) and high flux(268 L·m~(-2)·h~(-1)) at 0.1 MPa and ambient temperature. MXene endows the membrane with much water channel and denser functional layer which improves the membrane performance obviously. The membrane shows excellent solvent resistance to dimethylformamide(DMF), acetone and methanol after crosslinking with TETA during the 18 days of immersion.     

Simultaneous recovery of phosphorus and nitrogen from liquid digestate by vacuum membrane distillation with permeate fractional condensation

A vacuum membrane distillation(VMD) process with permeate fractional condensation on membrane downstream has been developed for simultaneous recovery of phosphorus and nitrogen from liquid digestate. The polytetrafluoroethylene(PTFE) membrane flux could reach 6000 g·m~(-2)·h~(-1) with the rejection efficiency of total phosphorus(TP) over 0.99, under the condition of flowrate being 120 L·h~(-1) and temperature being 40°C. Membrane fouling occurred with a film of organics and microorganism deposited on the surface of the membrane. Membrane flux could be reversed after the membrane was rinsed by water. Higher feed temperature and flowrate could improve the membrane flux, while hardly affect the rejection efficiency of total phosphorus. The concentration of TP could reach 1600 mg·L~(-1) after membrane distillation, which is about 5 times of that in initial liquid digestate. On the downstream of the membrane, some of the permeate vapor was condensed under the vacuum condition and most of water was collected here. The remaining vapor enriched with total nitrogen(TN) was compressed and pumped to the atmospheric condition to condense. The TN concentration in atmospheric condensate was as high as 7000 mg·L~(-1) with the process separation factor for ammonia being enhanced to 114.     

Preparation and performance of novel thermal stable composite nanofiltration membrane

The novel thermal stable composite nanofiltration membranes were prepared through the interfacial polymerization of piperazine and trimesoyl chloride on the poly (phthalazinone ether) ultrafiltration substrate. The effects of polymerization and testing conditions on membrane performance were studied. The surface morphologies of the substrate and the composite membranes were observed by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). The separation properties of membranes for dyes and salts were tested. The composite membranes show good thermal stability. The rejection for Na₂SO₄ was kept over 96%, while the flux reached 400 L·m^-2·h^-1 when it was tested at 1.0 MPa and 80°C. When tested at 1.0 MPa and 60°C, the rejection of the composite membrane for dyes was kept at high level, and the flux reached 180–210 Lm^-2·h^-1, while the rejection for NaCl was lower than 20%.     

Effect of ethylene vinyl acetate content on the performance of VMD using HDPE co-blending membrane

Membranes were fabricated with high-density polyethylene(HDPE) and ethylene vinyl acetate(EVA) blend through thermally induced phase separation and were then used for vacuum membrane distillation(VMD).The membranes were supported by nonwoven polyester fabric with a special cellular structure. Different membrane samples were obtained by adjusting the polymer concentration, HDPE/EVA weight ratio, and coagulation bath temperature. The membranes were characterized by scanning electron microscopy(SEM) analysis, contact angle test, and evaluation of porosity and pore size distribution. A series of VMD tests were conducted using aqueous NaCl solution(0.5 mol·L~(-1)) at a feed temperature of 65 ℃ and permeate side absolute pressure of 3 kPa. The membranes showed excellent performance in water permeation flux, salt rejection, and long-term stability. The HDPE/EVA co-blending membranes exhibited the largest permeation flux of 23.87 kg·m~(-2)·h~(-1) and benign salt rejection of ≥99.9%.     

Plant-inspired biomimetic hybrid PVDF membrane co-deposited by tea polyphenols and 3-amino-propyl-triethoxysilane for high-efficiency oil-in-water emulsion separation

Membrane pollution caused by separating oily wastewater is a big challenge for membrane separation technology. Recently, plant-/mussel-inspired interface chemistry has received more and more attention. Herein, a high antifouling poly (vinylidene fluoride) (PVDF) membrane, coated with tea polyphenols (TP, extracted from green tea) and 3-amino-propyl-triethoxysilane (APTES), was developed to purify oil-in-water emulsions. ATR-FTIR, XPS and SEM were used to demonstrate the evolution of surface biomimetic hybrid coatings. The performances of the developed membranes were investigated by pure water permeability and oil rejection for various surfactant-stabilized oil-in-water emulsions. The experimental results revealed that the membrane deposited with a mass ratio of 0.1/0.2 exhibited ultrahigh pure water permeability (14570 L·m^-2·h^-1·bar^-1, 1 bar=0.1 MPa) and isooctane-in-water emulsion permeability (5391 L·m^-2·h^-1·bar^-1) with high separation efficiency (>98.9%). Even treated in harsh environment (acidic, alkaline and saline) for seven days, the membrane still maintained considerable underwater oleophobic property (148°–153°). The fabricated plant-inspired biomimetic hybrid membranes with excellent performances light a broad application prospect in the field of oily wastewater treatment.     

Design and synthesis of Al-MOF/PPSU mixed matrix membrane with pollution resistance

To enhance the performance of the polyphenylene sulfone(PPSU) membrane,a novel mixed matrix membrane with hydrophilicity and antifouling properties was prepared.Using PPSU as the ba sic membrane material,polyvinyl pyrrolidone(PVP) as the porogen,N-Methyl pyrrolidone(NMP) as the solvent,and MOF-CAU-1(Al_4(OH)_2(OCH_3)_4(H_2 N-BDC)_3·xH_2 O) as the filler,PPSU/CAU-1 mixed matrix membrane(MMM) was prepared by an immersion precipitation and phase transformation technique.By changing the amount of MOF-CAU-1,the properties and performance of the MMM membrane were investigated in terms of hydrophilicity,pore morphology,surface roughness,and dye removal.The results show that the highest pure water flux of the mixed reached 47.9 L·m~(-2)·h~(-1), when the CAU-1 addition amount was 1.0 wt%, which was 23% higher than that of the pure PPSU membrane.Both the rejection rate and the antifouling performance of the MMM membrane also noticeably improved.     

Fabrication of anti-fouling polyamide nanofiltration membrane by incorporating streptomycin as a novel co-monomer

Polyamide (PA) thin-film composite (TFC) nanofiltration (NF) membrane has extremely broad application prospects in separation of monovalent/divalent inorganic salts mixed solution. However, membrane fouling is the main obstacle to the application of PA, TFC and NF membrane. Streptomycin (SM) is a hydrophilic antibiotic containing a large number of hydroxyl and amino groups. In this work, the NF membrane was prepared via interfacial polymerization (IP) between trimesoyl chloride (TMC) in the organicphaseand SM/piperazine (PIP) mixture in theaqueousphase. The NF membrane structure and performance were characterized in detail. The results showed that SM successfully participated in the IP. The negative charge and hydrophilicity of membrane surface were improved. The prepared membrane exhibited good anti-adhesion and anti-bacterial performance. Additionally, when the SM concentration was 2%, the prepared membrane exhibited the optimal permselectivity. The water permeance was 89.4 L·m^-2·h^-1·MPa^-1. The rejection of NaCl and Na₂SO₄ were 17.17% and 97.84%, respectively. The NaCl/Na₂SO₄ separation factor of the SM2-PIP/TMC membrane in 1000 mg·L^-1 NaCl and 1000 mg·L^-1 Na₂SO₄ mixed solution was 40, which was 3.3 times that of PIP/TMC membrane. It indicated that SM2-PIP/TMC demonstrated excellent monovalent/divalent salts separation performance. This work provided an easy and effective approach to preparing anti-fouling NF membrane while possessing superior monovalent/divalent salts separation performance.     

Towards superior permeability and antifouling performance of sulfonated polyethersulfone ultrafiltration membranes modified with sulfopropyl methacrylate functionalized SBA-15

A non-solvent induced phase separation (NIPS) process was used to fabricate a series of sulfonated polyethersulfone (SPES) membranes blending with different concentrations of SBA-15-g-PSPA with the applications in the ultrafiltration (UF) process. SBA-15 was modified with 3-methacrylate-propyltrimethoxysilane (MPS) to form SBA-15-g-MPS. It was further modified with the charge tailorable polymer chains by reacting with 3-sulfopropyl methacrylate potassium salt. The nanoparticles were uniformly dispersed and finger-like channels were developed within the membrane. The adding of surface modified SBA-15-g-PSPA nanoparticles has significantly improved membrane water permeability, hydrophilicity, and antifouling properties. The pure water fluxes of the composite SPES membranes were significantly higher than the pristine SPES membrane. For the membrane containing 5% (mass) of SBA-15-g-PSPA (MSSPA5), the pure water flux was increased dramatically to 402.15 L·m^-2·h^-1, which is ~1.5 times that of MSSPA0 (268.0 L·m^-2·h^-1). The high flux rate was achieved with 3% (mass) of SBA-15 nanoparticles with retained high rejection ratio 98% for natural organic matter. The results indicate that the fashioned composite membrane comprising SBA-15-g-PSPA nanoparticles have a promising future in ultrafiltration applications.     

Regulatable pervaporation performance of Zn-MOFs/polydimethylsiloxane mixed matrix pervaporation membranes

Pervaporation (PV) is an emerging separation technique for liquid mixture. Mixed matrix membranes (MMMs) often demonstrate trade-off relationship between separation factor and flux. In this study, by changing the organic linkers (2-methyl imidazolate, imidazole-2-carboxaldehyde, 2-ethyl imidazolate), ZIF-8, ZIF-90 and MAF-6 were prepared and filled in polydimethylsiloxane (PDMS) membranes for dealcoholization of 5% (mass) n-butanol solution, and the membranes properties and pervaporation performances were adjusted. Compared with the pure PDMS membrane, the addition of ZIF-8 resulted in a 9% increase in flux (1136 g·m^-2·h^-1) and a 22.5% increase in separation factor (28.3), displaying anti-trade-off effect. For the MAF-6/PDMS MMMs (2.0% mass loading), the pervaporation separation index (PSI) and separation factor were 32347 g·m^-2·h^-1 and 58.6 respectively (increased by 34% and 154% in contrast with that of the pure PDMS membrane), and the corresponding permeation flux was 552 g·m^-2·h^-1, presenting great potential in the removal butanol from water. It was deduced that the large aperture size combined with moderate hydrophobicity of metal-organic frameworks (MOFs) favor the concurrent increase in permeability and selectivity.     

引入天然黏合剂作为黏合层的复合膜用于渗透蒸发乙醇脱水(英文)

A high performance composite membrane was prepared under the inspiration of bioadhesion principles for pervaporative dehydration of ethanol. Chitosan (CS) and polyacrylonitrile (PAN) ultrafiltration membranes were used as the active layer and the support layer, respectively. Guar gum (GG), a natural bioadhesive, was in-troduced as the intermediate bonding layer to improve the separation performance and stability of the fabricated CS/GG/PAN composite membranes. The contact angle of the GG layer was just between those of the CS layer and the PAN layer, minimizing the difference of hydrophilicity between the active layer and the support layer. The peeling strength of the composite membrane was significantly enhanced after the introduction of the GG layer. The effects of preparation conditions and operation conditions including GG concentration, operating tempera-ture and ethanol concentration in feed on the pervaporation performance were investigated. The as-fabricated CS/GG/PAN composite membrane showed the optimum performance with a permeation flux of up to 804 g·m?2·h?1 and a separation factor higher than 1900. Besides, the composite membranes exhibited a desir-able long-term operational stability.     

Enhancing the separation performance by introducing bioadhesive bonding layer in composite pervaporation membranes for ethanol dehydration

A high performance composite membrane was prepared under the inspiration of bioadhesion principles for pervaporative dehydration of ethanol. Chitosan (CS) and polyacrylonitrile (PAN) ultrafiltration me...     

Improvement of porous polyvinylidene fluoride-co-hexafluropropylene hollow fiber membranes for sweeping gas membrane distillation of ethylene glycol solution

Porous polyvinylidene fluoride-co-hexafluropropylene (PVDF-HFP) hollow fiber membranes were fabricated through a wet spinning process. In order to improve the membrane structure, composition of the polymer solution was adjusted by studying ternary phase diagrams of polymer/solvent/non-solvent. The prepared membranes were used for sweeping gas membrane distillation (SGMD) of 20 wt% ethylene glycol (EG) aqueous solution. The membranes were characterized by different tests such as N₂ permeation, overall porosity, critical water entry pressure (CEP_w), water contact angle and collapsing pressure. From FESEM examination, addition of 3 wt% glycerol in the PVDF-HFP solution, produced membranes with smaller finger-likes cavities, higher surface porosity and smaller pore sizes. Increasing the polymer concentration up to 21 wt% resulted in a dense spongy structure which could significantly reduce the N₂ permeance. The membrane prepared by 3 wt% glycerol and 17 wt% polymer demonstrated an improved structure with mean pore size of 18 nm and a high surface porosity of 872 m^-1. CEP_w of 350 kPa and overall porosity of 84% were also obtained for the improved membrane. Collapsing pressure of the membranes relatively improved by increasing the polymer concentration. From the SGMD test, the developed membrane represented a maximum permeate flux of 28 kg·m^-2·h^-1 which is almost 19% higher than the flux of plain membrane. During 120 h of a long-term SGMD operation, a gradual flux reduction of 30% was noticed. In addition, EG rejection reduced from 100% to around 99.5% during 120 h of the operation.     

无机杂化海藻酸钠渗透汽化膜的制备与分离性能对比

为提高海藻酸钠（SA）膜的渗透汽化分离性能,分别采用纳米氧化铝、纳米氧化锆和纳米氧化钛对SA膜进行改性,对比分析了3种不同杂化膜渗透汽化分离性能的差异,并将分离性能较好的杂化膜应用到乙酸与乙醇酯化反应脱水的体系中。系统考察了无机纳米粒子含量对SA膜渗透汽化分离性能的影响,对杂化膜进行了接触角、傅里叶红外（FTIR）、扫描电子显微镜（SEM）、热重/差示扫描量热（TG/DSC）、X射线衍射（XRD）和拉伸强度等表征与分析。结果表明,无机纳米粒子能提高SA膜的热稳定性、机械强度和渗透通量,当无机纳米粒子与SA质量比为0.3时,掺杂TiO₂、ZrO₂和Al₂O₃的杂化膜二碘甲烷的接触角依次升高,同时渗透通量也依次升高。SA-0.3Al₂O₃杂化膜亲水性较好,然而SA-0.3ZrO₂杂化膜分离性能最优,50℃下分离水含量10%的乙醇-水溶液,膜渗透通量达到336 g·m^-2·h^-1,渗透侧水含量99.97%,分离因子29990。酯化反应脱水实验表明,在80℃时,酯化反应脱水实验乙酸转化率均高于无脱水实验乙酸转化率,平衡转化率不断被打破,反应12 h后,转化率由平衡时的79.3%提高到93.9%。     

Hydrophobic modification of SAPO-34 membranes for improvement of stability under wet condition

SAPO-34 zeolite membranes show high efficiency for CO₂/CH₄ separation but suffer from the reduction of separation performance when exposed to humid atmosphere. In this work, n-dodecyltrimethoxysilane (DTMS) was used to modify the hollow fibers supported SAPO-34 membranes to increase the external surface hydrophobicity and thus sustain their performance under moisture environment. The modified membranes were fully characterized. Their separation performance was extensively investigated in both dry and wet gaseous systems and compared with the un-modified ones. The un-modified SAPO-34 membrane exhibited a high separation selectivity of 160 and CO₂ permeance of 1.18×10^-6 mol·m^-2·s^-1·Pa^-1 for separation of dry CO₂/CH₄ at 298 K. However, its separation selectivity declined to 0.9 and the CO₂ permeance was only about 1.7×10^-8 mol·m^-2·s^-1·Pa^-1 for wet CO₂/CH₄ at same temperature. High temperature (e.g. 353 K) could reduce the effect of moisture to improve SAPO-34 separation selectivity, but further increasing temperature (e.g. 373 K) led to decrease in CO₂/CH₄ separation selectivity. A significant decrease of selectivity was observed at higher pressure drop. The modified SAPO-34 membrane showed decreased CO₂ permeance but increased separation selectivity for dry CO₂/CH₄ gas mixture, and super performance for wet CO₂/CH₄ gas mixture due to the improved hydrophobicity of membrane surface. A separation selectivity of 65 and CO₂ permeance of 4.73×10^-8 mol·m^-2·s^-1·Pa^-1 for wet CO₂/CH₄ mixture can be observed at 353 K with a pressure drop of 0.4 MPa. Furthermore, the modified membrane exhibited stable separation performance during the 120-hour test for wet CO₂/CH₄ mixture at 353 K. The hydrophobic modification paves a way for SAPO-34 membranes in real applications.     

涂覆法制备高性能磺化聚醚砜混合基质膜

采用涂覆法将磺化聚醚砜（SPES（浓度为0.7%（质量（的铸膜液制备成膜，并使用钛酸四丁酯（TBT（和TiO₂纳米颗粒作为添加剂来对比改善膜性能。通过对纳滤膜的微观结构表征，以及膜对NaCl与染料的分离性能等方面来分析其性能。当钛酸四丁酯的含量为0.35%（质量（时，膜的通量从27.3 L·m^-2·h^-1提升至38.9 L·m^-2·h^-1，而截留率则有91.2%降至82.5%。与纯SPES膜相比，改性纳滤膜的平均孔径更大，由1.51 nm增大为2.28 nm。TBT改性膜表面有TiO₂纳米颗粒形成，而且随着TBT的浓度增大，颗粒逐渐增大，而直接添加TiO₂纳米颗粒的纳滤膜的表面呈现明显的团聚现象。使用钛酸四丁酯代替TiO₂纳米颗粒作为添加剂，在增加膜通量的同时也能降低纳米颗粒团聚而导致的膜缺陷。由钛酸四丁酯水解生成的正丁醇的致孔作用对膜的性能具有很大的影响。     

超亲水SiO2修饰膜的构建及其油水乳液分离性能

采用硅溶胶和多巴胺作为修饰剂,通过一步反应在微孔聚丙烯膜(MPPM)表面构建了SiO₂修饰层。利用FTIR、ESEM和EDX对膜进行了表征,发现膜表面SiO₂颗粒分布非常均匀。水/油接触角及纯水通量实验结果表明,修饰膜具有超亲水性及水下超疏油性,透水能力强,水通量大[在0.1 MPa时,水通量高达(5100±500)L·m^-2·h^-1]。油水乳液分离结果表明,修饰膜能有效分离油水乳液,在0.05 MPa时,油水乳液水通量达2830 L·m^-2·h^-1,油截留率达99.8%以上,即使过膜压力增大到0.15 MPa,油截留率也能保持在99%以上,且膜表面的油污可用水清洗除去,展现出很好的应用前景。     

Al2O3和SiC微滤膜的疏水改性及其油固分离性能研究

以正辛基三乙氧基硅烷和乙醇分别作为改性剂和溶剂,采用接枝聚合法对平均孔径为500 nm的Al₂O₃膜和SiC膜进行疏水改性,考察了改性剂浓度、改性液温度和改性时间对膜表面疏水效果的影响,并对比了疏水改性前后两种陶瓷膜的表面性质及疏水改性后的油固分离性能,进行了反冲实验和稳定性测试。结果表明,两种陶瓷膜材料在改性剂浓度为0.2 mol·L^-1,改性液温度为40℃,改性时间为12 h时,疏水改性效果最好,得到的疏水Al₂O₃膜和SiC膜的水接触角分别为134°±1°和140°±1°,经改性后的SiC膜的疏水效果优于Al₂O₃膜。在油固分离实验中,疏水Al₂O₃膜和SiC膜均对固体炭黑有良好的截留性能,但疏水改性对SiC膜的油品通量提升更为显著,两种膜的稳态通量分别为1134 L·m^-2·h^-1和1408 L·m^-2·h^-1。反冲操作对疏水SiC膜的通量恢复更有利。     

添加剂和凝结剂温度对用无溶剂致相位分离法生产高性能PVDF/聚醚F127混合中空光纤膜的影响(英文)

Poly(vinylidene fluoride)(PVDF) has become one of the most popular materials for membrane prepara-tion via nonsolvent induced phase separation(NIPS) process.In this study,an amphiphilic block copolymer,Plu-ronic F127,has been used as both a pore-former and a surface-modifier in the fabrication of PVDF hollow fiber membranes to enhance the membrane permeability and hydrophilicity.The effects of 2nd additive and coagulant temperature on the formation of PVDF/Pluronic F127 membranes have also been investigated.The as-spun hollow fibers were characterized in terms of cross-sectional morphology,pure water permeation(PWP),relative molecular mass cut-off(MWCO),membrane chemistry,and hydrophilicity.It was observed that the addition of Pluronic F127 significantly increased the PWP of as-spun fibers,while the membrane contact angle was reduced.However,the size of macrovoids in the membranes was undesirably large.The addition of a 2nd additive,including lithium chlo-ride(LiCl) and water,or an increase in coagulant temperature was found to effectively suppress the macrovoid for-mation in the Pluronic-containing membranes.In addition,the use of LiCl as a 2nd additive also further enhanced the PWP and hydrophilicity of the membranes,while the surface pore size became smaller.PVDF hollow fiber with a PWP as high as 2530 L?m?2?h?1?MPa?1,a MWCO of 53000 and a contact angle of 71° was successfully fabricated with 3%(by mass) of Pluronic F127 and 3%(by mass) of LiCl at a coagulant temperature of 25 °C,which shows better performance as compared with most of PVDF hollow fiber membranes made by NIPS method.     

聚偏氟乙烯/聚二甲基硅氧烷渗透气化膜在丁醇分离中的应用

通过相转化法制备PVDF多孔支撑膜,在其上涂覆致密的PDMS分离层制备得到PVDF/PDMS复合膜,用于丁醇的分离纯化。以丁醇水溶液为原料液,流速为1.6 L·min^-1,丁醇浓度为15 g·L^-1,温度为37℃时, PVDF/PDMS复合膜的总通量为158.2 g·m^-2·h^-1,分离因子为17.3。向丁醇水溶液中按丁醇：丙酮：乙醇比例为6：3：1添加丙酮和乙醇模拟发酵液,PVDF/PDMS复合膜的总通量升高到189.5 g·m^-2·h^-1,分离因子降低到14.8。进一步考察了以丙酮-丁醇-乙醇（ABE）发酵液为原料液的渗透气化膜分离性能,发酵液中不存在菌体时,PVDF/PDMS复合膜的总通量和分离因子分别为120.2 g·m^-2·h^-1和19.7,而菌体存在时,复合膜的总通量和分离因子分别为122.1 g·m^-2·h^-1和16.7。与PDMS均质膜相比,PVDF/PDMS复合膜在丁醇分离过程中的分离性能有了显著的提升, 具有潜在的应用价值。     

Negatively charged organic–inorganic hybrid silica nanofiltration membranes for lithium extraction

Effective extraction of lithium from high Mg~(2+)/Li+ratio brine lakes is of great challenge. In this work, organic–inorganic hybrid silica nanofiltration(NF) membranes were prepared by dip-coating a 1,2-bis(triethoxysilyl)ethane(BTESE)-derived separation layer on tubular TiO_2 support, for efficient separation of LiC l and MgCl_2 salt solutions. We found that the membrane calcinated at 400 °C(M1–400) could exhibit a narrow pore size distribution(0.63–1.66 nm) owing to the dehydroxylation and the thermal degradation of the organic bridge groups. All as-prepared membranes exhibited higher rejections to LiCl than to MgCl_2, which was attributed to the negative charge of the membrane surfaces. The rejection for LiCl and MgCl_2 followed the order: LiCl N MgCl_2, revealing that Donnan exclusion effect dominated the salt rejection mechanism. In addition, the triplecoated membrane calcined at 400 °C(M3–400) exhibited a permeability of about 9.5 L·m~(-2)·h~(-1)·bar~(-1) for LiCl or MgCl_2 solutions, with rejections of 74.7% and 20.3% to LiCl and MgCl_2,respectively, under the transmembrane pressure at 6 bar. Compared with the previously reported performance of NF membranes for Mg~(2+)/Li+separation, the overall performance of M3–400 is highly competitive. Therefore, this work may provide new insight into designing robust silica-based ceramic NF membranes with negative charge for efficient lithium extraction from salt lakes.